1. Field of the Invention
This invention relates to a lock assembly for a roll-up door and to a gate locking system providing a high degree of protection from unauthorized entry, while being simple and quick to operate. More particularly, the present invention relates to a system for locking a gate movable between opposed tracks in a closed position providing a high degree of protection against burglary and being substantially self-contained such that its only removable part is its key.
2. Description of the Prior Art
Gate locking systems employed are security gates for factory doors, mall grills, store fronts, trucks and the like conventionally comprise opposed channel guide tracks and a gate movable within the tracks between open and closed positions. In high crime areas, the system must be capable of preventing unauthorized opening by both covert attacks (i.e., attempting to unlock the system without damaging it) and overt attacks (i.e., attempting to open the system by physically destroying it). Conventional gate locking systems are not able to provide adequate security against both covert and overt attacks, and are relatively expensive and difficult to manufacture and operate.
One conventional system is disclosed in U.S. Pat. No. 3,600,912 to Foreman. The Foreman arrangement comprises a sleeve which is fitted within aligned holes within the track and gate when the gate is closed, and a key cylinder with a threaded bolt which can only be turned to lock the sleeve in place when its key is in its key hole. A bracket is provided on the track for storing the parts when not in use. Thus, the Foreman system has a number of parts separable from the gate and track which have a tendency to become lost, and is difficult and time consuming to assemble and securely lock during the closing operation.
Another locking mechanism for this environment is disclosed in applicant's own U.S. Pat. No. 4,345,448, which patent is incorporated herein by reference. The system disclosed in such patent comprises a separable bracket and lock which must be mounted on a track and gate assembly to lock the gate. Thus, this system also requires parts which are separable from the track and gate and susceptible to being lost, and require considerable time to lock the assembly in aligning the bracket, mounting the lock and actuating the lock by the key.
The ability of the locking system to be self-contained and attached to the track, except for the key, prevents loss of portions of the locking assembly. The time required to assemble and actuate the lock is extremely critical since the store owner's or truck operator's exposure and susceptibility to robbery and burglary are at their highest level during the closing operation. Thus, it is extremely important that the locking mechanism operate to lock the gate in its closed position without searching for and aligning the various lock system parts and without using a key.